General examples of rotary slitter knives are to be found in U.S. Pat. No. 5,574,890 (Rackoff et al.) and U.S. Pat. No. 4,336,083 (Dempsey). For the purposes of providing background information, these patents are hereby incorporated by reference as if set forth in their entirety herein.
Typically, a pair of rotary knives, mounted on respective mounting rods (or "arbors"), will be located on opposite sides of a metal sheet as it is being passed between the knives. The two rotary knives, which are not directly opposite one another, will then converge on the metal sheet and, as long as they are in contact with the metal sheet, will create a shear fracture that serves to actually cut the metal sheet.
Several such knives will usually be located on each rod, separated by predetermined distances over the longitudinal extent of each rod, so as to enable the simultaneous cutting of the metal sheet into several narrower strips.
It is conventional to utilize metal spacers in between the rotary knives on each arbor, to establish and maintain predetermined distances between neighboring rotary knives on each arbor. However, several disadvantages have been noted in conjunction with conventional metal spacers.
Generally, metal spacers (usually steel spacers) have been found to be inordinately heavy, leading to problems such as wear on the arbors (from excessive loading). Furthermore, conventional metal spacers can be prone to damage and wear on their extreme edges or surfaces.